The purpose of this research is to investigate and develop the potential usefulness of photochemotherapy as an approach to the management of malignant tumors, particularly brain tumors. The overall objectives of this project are (1) to define the conditions necessary to develop selective destruction by exposure to light of tumor cells sensitized by hematoporphyrin in vitro and in vivo, (2) to develop suitable light sources for exciting intracellular hematoporphyrin and (3) to prepare purified hematoporphyrin for in vitro and in vivo experiments.